Conventionally, in a transceiver for a vehicle which is used for remote control for unlocking a vehicle door or the like, a transceiver for a vehicle for preventing a vehicle theft or the like is known. An example thereof is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 4-336185.
As shown in FIG. 6, in this transceiver for a vehicle, data including a variable code (which is also called a rolling code) corresponding to a number of times of operation (i.e., the total number of times a transmitter 70 is operated) is transmitted from the transmitter 70, which is provided at a wireless door lock remote controller, to a receiver 72 provided at a vehicle. At the receiver 72, when a fixed code of the received data matches the code of the receiver 72 and the rolling code and the number of times of receipt matches each other, specifically, when the rolling code of the transmitter 70 and the value of a rolling counter of the receiver 72, which is synchronous with the rolling code match, the receiver 72 receives the transmitted data. Accordingly, for example, when another person operates the transmitter 70 several times without pointing the same toward the vehicle, and thereafter operates the transmitter 70 while pointing the same toward the receiver 72 of the vehicle, because the rolling code and the number of times of receipt do not match, the receiver 72 does not receive the transmitted data However, when the owner of the vehicle operates the transmitter 70 several times while mistakenly riot pointing the same toward the vehicle, and thereafter operates the transmitter 70 while pointing the same toward the receiver 72 of the vehicle, the number of times of receipt by the receiver 72 is jump-updated by a predetermined operation (i.e., the number of times of receipt, which is the number of times the transmitter 70 was operated without being pointed toward the vehicle, is added) so that the receiver 72 can receive the transmitted data.
However, in this transceiver for a vehicle, when a battery of the transmitter becomes weak or the like, there is the possibility that transmission data into which an incorrect rolling code has been written may be generated at and transmitted by the transmitter. In this case, even if the number of times of receipt by the receiver 72 is jump-updated by a predetermined operation, there is the possibility that the rolling code and the number of times of receipt will not match.
In view of the aforementioned, it is an object of the present invention to provide a transceiver for a vehicle and a transmitting-receiving method thereof in which errors in the transmission of a rolling code can be prevented.